Control valve for hydraulic presses



NOV. 14, 1944. TOWLER 2,362,864

CONTROL VALVE FOR HYDRAULIC PRESSES Filed March 30, 1942 I 2Sheets-Sheet 1 Nov. 14, 1944. J. M. TOWLER 2,362,854

I CONTROL VALVE FOR HYDRAULIC PRESSES Filed March so, 1942 2Sheets-Sheet 2 zs I A Z rmQA/Ey Patented Nov. 14.1944

2,362,884 CONTROL VALVE FOR HYDRAULIOPBESSES John Maurice Towler,Yorkshire, England Application March; so, 1942, Serial No. 438,823 InGreat Britain March 1, 1941 '7 Claims.

This invention relates to control valves for hydraulic presses.

'If the control valve connected to a comparatively large hydraulic pressis suddenly opened to exhaust, it will cause a sudden surge of pressurein the exhaust main due to the sudden release of the hydraulic energystored in the press. The object of this invention is to provide anauxiliary valve having means which automatically control the release ofpressure from the press cylinder so as to prevent any sudden surge ofpressure in the exhaust main, no matter how the control valve isoperated.

The present invention consists broadly of a valve for controlling therelease of pressure liquid from a hydraulic press to exhaust, said valvecomprising a main outlet which permits of a sudden release of pressureliquid from the press and a subsidiary outlet of restricted area whichpermits of a gradual release f pressure liquid from the press and valvemeans controlling the escape of liquid through said main outlet saidvalve means operating automatically to close the main outlet when apredetermined pressure of the liquid in the press is reached whereby theinitial release of pressure liquid from the press occurs graduallythrough the restricted subsidiary outlet, and to open the main outlet topermit of a sudden release of the pressure from the press when thepressure of said liquid falls to a predetermined safe level.

A control valve according to a preferred embodiment of the inventioncomprises a transferpassage, an inlet for the delivery to said transferpassage of pressure liquid from a pump or accumulator, communicationstransfer passage on the one hand with the hydraulic press and on theother hand with exhaust, an automatically operating valve for openingand closing the communication between the hydraulic press and thetransfer passage, a further valve for closing and opening thecommunication between the transfer passage and exhaust and a subsidiaryor branch passage of restricted area for by-passing the automaticallyoperating valve which opens and closes the communication between thetransfer passage and the hydraulic press the arrangement being such thatduring the delivery of pressure liquid from the pump or accumulator tothe press the connection between the transfer passage and exhaust isclosed by its valve whilst the other connection between the transferpassage and the press is open until a predeterminedpressure of liquid inthe press is attained when the valve controlling said comconnectingsaidmunication is automatically closed and on operation of the valve toopen the connection between the transfer passage and exhaust pressureliquid passes from the hydraulic press to the transfer passage forescape to exhaust through the subsidiary or branch passage to ensurethat the initial release of pressure liquid from the press to exhaustoccurs gradually until such time as the pressure of said liquid falls toa safe level when the automatically operating valve opens to permit offull and sudden release of said pressure liquid from the press toexhaust.

A control valve according to the above preferred embodiment alsoincludes an automatically operating non-return valve for permittingdelivery of liquid from the pump or accumulator to the press when theautomatically operating valve associated with the communication betweenthe press and the transfer passage is closed. Such non-return valve ispreferably a separate valve but it may also be constituted by the lowerend of the first mentioned automatically operating valve by making thelower part of said latter valve separate from the upper portion thereofso that when the upper part is moved by the pressure liquid away fromthe lower portion, said lower portion is free to open to pass pressureliquid to the press.

In order that the invention may be clearly understood and carried intoeflect a control valve according to two embodiments of the inventionwill now be described as examples by aid of the accompanying drawings inwhich:

Fig. 1 is a cross section through a valve according to the inventionshowing the use of a nonreturn valve of the disc type.

Fig. 2 is a similar view of the valve but showing the use of anon-return valve of the mitre type.

In the valve illustrated in the drawings the valve body l'is machined toprovide two parallel bores 2 and 3 in each of which slides a closelyfitting valve plunger 4 and "5 respectively, of the packingless pistontype. These two bores are intersected near their lower ends by atransverse transfer passage 8 which has an inlet 'I at one end for theadmission of pressure liquid from an hydraulic pump or accumulator.

The lower endsof the bores 2 and 3 open into chambers 8 and 8respectively and these in turn communicate, in the case of chamber 8,with the press cylinder through an opening l0 and in the case of chamber9, the exhaust main, through an opening H. The communicating openingsbetween the transfer passage 6 and the chambers 8 and 9 are thereforeconstituted by the lower portions of the bores 2 and. 3 and for the sakeof clarity these are indicated on the drawings by the references 2a andla respectively. Such openings are closable by the lower ends 4a and 5a.of the valve plungers 4 and I when said plungers are in their raisedpositions, said lower ends being separated from the upper and main partof the plungers by reduced portions I2 and i2.

As shown in the drawings the plunger 4 is in its lowest position and theplunger I in its raised position. The transfer passage 4 is thereforeclosed to exhaust by reason of the portion Ia of the plunger 5 residingwithin the lower bore in and open to the press by reason of the portion4a of the plunger 4 being below and clear of the bore 2a. Pressureliquid entering through inlet 1 is therefore permitted to pass directlyto the press cylinder for operating the press.

Pressing against the upper end of the plunger 4 is a spring l4 which isloaded so as to hold the plunger in the open and lowered position shownagainst all pressures in the press cylinder below a predeterminedmaximum. When this maximum pressure is reached the valve plunger isforced upwards to compress the spring and close the lower bore 2a.

So that the pump or accumulator shall continue to deliver pressureliquid to the press cylinder after the valve plunger 4 has lifted to theclosed position, an alternative passage for the liquid between thetransfer passage 8 and the chamber 8 is provided, which passage isclosable against the reverse flow of pressure liquid by a non-returnvalve.

In the example illustrated in Fig. 1 this alternative passage isconstituted by holes II in the lower portion 4a. of the plunger 4 whilstthe nonreturn valve is of the disc type and consists of a flexiblewasher l6, seating against the'lower face of the portion 4a so as toclose the holes i 5 In the modification illustrated in Fig. 2 a mitretype non-return valve I1 is used. This valve is located in ,a recess orchamber l8 and serves to close the inner end of a passage I! connectingthe chamber ill with the transfer passage 8. The connection between thechamber l8 and the passage 6 is constituted by the right angled port orpassage 20.

The valve plunger 5, which constitutes the main control valve, includesa stem 23 slidable within the reduced bore 24, the upper end of the stembeing headed or flanged, as at 25; an expansion spring 26 is interposedbetween'the head 25 and the top of the valve mechanism housing, the headbeing threaded upon the end of the stem 23, to permit of the location ofthe spring in surrounding engagement with the stem. A bifurcated bracket21, bolted to the housing as at 28, serves as a mounting for the camlever 29, as at 29. As the cam lever is actuated toward the housing, thevalve is urged to seated position (as shown) in opposition to the spring26, the movement of the cam lever in the reverse direction permittingthe valve to move under the influence of said spring to open the passage3a between the delivery passage 6 and the chamber 9. A stop 30 isprovided to limit the movement of the lever toward the housing to insureaccuracy in the seating of the valve. With the main control plunger inthe raised position shown the delivery from the pump or accumulatorpasses directly to the press cylinder to force the press ram against thework. As compression of the work proceeds the resistance to the movementof the ram will increase and in consequence the pressure of the liquidin'the press cylinder will rise. When this pressure reaches apredetermined figure, herein referred to as the pressure at which theliquid may with safety be permitted rapidly to exhaust, it overcomes theresistance of the spring l4 and forces the plunger 4 upwards to closethe passage 2a. Pressure liquid is still permitted to pass to the presscylinder but it is now constrained to flow through the alternativepassage and past the non-return valve.

When the pressure stroke of the press ram is completed the control valveplunger 5 is moved downwards to open the passage in and so place theinterior of the transfer passage 6 in communication with exhaust. Thedelivery from the pump or accumulator now passes directly to exhaustthrough the open passage 3a. The sudden escape of liquid from the presscylinder to exhaust is however prevented by the previous closure of thepassage 2a by the raised plunger portion 4a. A gradual escape is howeverprovided for by the provision of a chocked or restricted by-passpassage, comprising a branch pipe 2| having in its length a choke,generally indicated at 22. This pipe connects the chamber 8 with thetransfer passage 6 and permits the liquid from the press cylinder toescape gradually at a regulated rate until the pressure in the presscylinder and the chamber 8 falls to a level at which it may with safetybe suddenly released into the exhaust main. At this lower pressure thespring is permitted to return the plunger to its lowered position, thusopening the non-restricted passage 2a and permitting the liquid to passrapidiy to exhaust.

In practice it is preferred to use as valve members plungers of thepackingless piston type but the invention is not to be limited by thisstated preference as any suitable valve means may be used which arecapable satisfactorily of controlling the escape of liquid from a pressso that a gradual initial release takes place when i the pressure in thepress exceeds a predetermined maximum as hereinafter defined in theclaims.

It is also to be understood that the main valve in the form of a singleacting plunger 5 is not an essential part of the invention as in thisform it is unsuitable for use where the pressure liquid is supplied froman accumulator as it does not provide for a cutting off of the supplyfrom the accumulator. Even where the pressure liquid is supplied by apump, this main control valve would very often be of the double-actingtype.

What I claim is:

1. A control valve for hydraulic presses comprising a housing having atransfer passage, an inlet for the delivery to said transfer passage ofpressure liquid from a source of supply, a bore connecting with saidtransfer passage and connectable to the hydraulic press, a second boreparallel to the first bore, communicating with the transfer passage andconnectable to the exhaust, an automatically operating valve in saidfirst bore for closing and opening the communication between thetransfer passage and the hydraulic press, a valve in the second bore forclosing and opening the communication between the transfer passage andthe exhaust, a branch passage of restricted area for by-passing theautomatically operating valve when operative to close the communicationbetween the transfer passage and the hydraulic press, and an autoofliquid in the press is attained, when said first-mentioned valvecontrolling such communication is automatically seated, the liquidcontinuing to flow to the press past said non-retum valve until fullpressure is applied to the press and the communication between thetransfer passage and the exhaust is opened by the actua- -tion of thevalve in said second bore to permit the liquid to pass from thehydraulic press to the transfer passage for escape to exhaust throughsaid branch passage, to ensure that the initial release of pressureliquid from the press to exhaust occurs gradually until such time as thepressure of said liquid falls to a safe level, when the automaticallyoperating valve in the first bore opens to permit of full and suddenrelease of said pressure liquid from the press to the exhaust.

2. A valve mechanism for controlling the release of pressure liquid froma hydraulic press to an exhaust, including a housing having a bore, achamber communicating with the lower end of said bore, said chamberhaving an outlet connectable to the exhaust, a second bore parallel tothe first bore, 'a chamber communicating with the lower end of saidsecond bore provided with an outlet connectable to the press cylinder, apassage connecting said bores above the respective chambers, saidpassage being connectable to a source of pressure liquid supply, amanually actuatable valve adjustable within said first bore to closecommunication between said bore and the exhaust through the chamberassociated with said first bore, a valve in said second bore, meanscooperating there with to render such valve normally responsive to thepressure fluid, when communication between said passage and the exhaustis closed, to maintain communlcation between said passage and the outletto the press cylinder, said latter valve being operable in response toan increase in the pressure of the liquid at a predetermined stage ofoperation of the press, to interrupt communication between said passageand the chamber associated with said second bore, and a by-pass betweensaid passage and the chamber connected to said bore to retard themovement of the pressure liquid from the latter chamber to the exhaust,when said firstvalve is actuated to open communication between saidpassage and the exhaust and communication between said passage and thechamber connectable to the press cylinder is closed by said secondvalve.

3. A valve mechanism for controlling the release of pressure liquid froma hydraulic press to an exhaust, including a housing having a bore, achamber communicating with the lower end of said bore, said chamberhaving an outlet conally actuatable valve adjustable within said firstbore to close communication between said bore and the exhaust throughthe chamber associated with said first'bore, a valvein said second bore,to close the area of communication between said passage and the chamberassociated with the second bore, liquid flow-controlling meansincorporated in said second valve adapted to yield to the pressureexerted by the liquid flowing to the press in the functioning of saidlatter valve to close communication between said passage and the chamberhaving an outlet to the press cylinder, to permit of the transfer of theliquid from said'passage to the latter chamber through said second valvein a reduced amount, said liquid flow-controlling means becominginoperative when said second valve assumes its normal position formaintaining communication between said passage and the chamber outlet tothe press cylinder, and means for permitting the pressure liquid toby-pass said second valve to escape gradually to the exhaust when saidsecond valve is closed and the firstmentioned valve is actuated to opencommunication between said passage and the exhaust.

4. A valve mechanism for controlling the release of pressure liquid froma hydraulic press to an exhaust, including a housing having a bore, achamber communicating with the lower end of said bore and provided withan outlet connectable to the exhaust, a second bore parallel to thefirst bore, a chamber communicating with the lower end of said secondbore and provided with an outlet connectable to the press cylinder, apassage connecting said bores above the respective chambers, saidpassage being connectable to a source of pressure liquid supply, amanually actuatable valve in said first bore for closing communicationbetween said passage and the outlet to the exhaust, a valve in saidsecond bore, means for normally maintaining said valve open whencommunication between said passage and the outlet to the exhaust isclosed, to maintain communication between said passage and the outlet tothe press cylinder to insure fiow of the pressure liquid to the press,said valve being movable, in response to a predetermined increase in thepressure of the liquid, to

nectable to the exhaust, a second bore parallel I to the first bore, achamber communicating with the lower end of said second bore providedwith an outlet connectable to the press cylinder, a passage connectingsaid bores above the respective chambers, said passage being connectableto a source of pressure liquid supply, a manua closed position tointerrupt such communication, a subsidiary connection between saidpassage and said outlet to the press cylinder, a check-valve in saidsubsidiary connection for permitting transfer of the liquid to the pressin a reduced amount when the valve in said second bore is moved to itsclosed position, and a by-pass between the outlet to the press cylinderand said passage for the gradual release of the pressure liquid from thepress cylinder when the valve in the first bore opens to exhaust, untilthe pressure of the fluid is reduced sufliciently to permit the valve inthe second bore to return to its open position.

5. A valve mechanism for controlling the fiow of pressure liquid to andfrom a hydraulic cylinder, comprising a housing having a bore, an inletand an outlet respectively connected to a source of pressure liquidsupply and to the hydraulic cylinder, passages connecting said inlet andsaid outlet to said bore to provide a communication between said inletand said outlet for the flow of the pressure liquid to the cylinder, aplunger slidable in said bore and movable to a position for closing saidcommunication, through the bore, in response to a predetermined increasein the pressure of the liquid. a non-re- 4 aseasos turn valve carried bysaid plunger for permitting continued flow of the pressure liquid to thecylinder when the plunger moves to its closed position; said non-returnvalve automatically moving to a closed position to interrupt the supplyof pressure liquid to the cylinder when the desired maximum pressure isattained therein, and

a passage of restricted area to permit the pressure liquid to escapeslowly from the hydraulic cylinder past the plunger and the non-returnvalve to exhaust while said plunger and said nonreturn valve are intheir closed position.

6. A valve mechanism for controlling the flow of pressure liquid to andfrom a hydraulic cylinder comprising a housing having a bore, an inletand an outlet respectively connected to a source of pressure liquidsupply and to the hydraulic cylinder, passages connecting said inlet andsaid outlet to said bore, a plunger slidable in the bore, spring meansfor normally maintaining said plunger in an open position, a portion ofreduced diameter in said plunger to provide an annular space within thebore permitting free flow of the pressure liquid to the cylinder throughthe bore when the plunger is in its open position, said plunger beingmovable to a closed position in response to a predetermined increase inthe pressure of the liquid, a non-return valve carried by said plungerto permit continued flow of the pressure liquid to the cylinder when theplunger moves to its closed position, said non-return valve cooperatingwith the plunger to automatically close the communication between theinlet and the outlet through the bore when the pressure of the liquid inthe cylinder reaches the desired maximum,

and a passage or restricted area to permit presoi pressure liquid to andfrom a hydraulic cylinder, comprising a housing having a bore, an

10 inlet and an outlet respectively connected to a source of pressureliquid supply and to the hydraulic' cylinder, passages connecting saidinlet and said outlet to said bore, to provide a communication betweensaid inlet and said outlet 15 for the flow 01 the pressure liquid to thecylinder, a plunger slidable in said bore and embodying a valve portion,said plunger being movable to a position wherein said valve portioncloses said communication through the bore in re- 20 sponse to apredetermined increase in the pressure of the liquid, a passagetoy-passing said valve portion and communicating with said inlet andsaid outlet, a non-return valve in said passage opening to permitcontinued flow of the pressure 25 liquid to the cylinder when theplunger moves to its closing position, said non-return valveautomatically moving to a closed position when the pressure of theliquid in the cylinder reaches a predetermined amount, and a furtherpassage of 3 restricted area to permit pressure liquid from thehydraulic cylinder to escape slowly to exhaust while said plunger andsaid non-return valve are in their closed position.

JOHN MAURICE TOWLER.

